This invention relates generally to a yarn texturing air jet system and the products produced thereby. More specifically, the invention relates to the textured yarn products produced by a process of continuously drawing continuous filament synthetic polymeric yarn under controlled temperature conditions, air jet texturing the drawn yarn and then subjecting the textured yarn to saturated steam while restraining the yarn from shrinking during steam treatment.
Bulky or crimped yarns composed of continuous synthetic fiber-forming polymers such as polyester and polyamide can be produced by feeding yarn filaments with overfeed to an air jet texturizer to produce a large number of random loops or crimps in the yarn. The type and degree of texture in the product yarn produced by such techniques depends upon the amount of twist in the feed yarn and on the amount of overfeed in the texturizing jet. The product yarn is generally spooled under tension and this product generally has poor linear stability and high boiling shrinkage values. The yarns are characterized by the presence of many ring-like or crunodal loops at irregular intervals along the surface of the yarn and internally in the yarn bundle.
When prior air jet texturing techniques according to the above are employed, a certain number of unstable or "wild" loops are generated in a random fashion along the yarn. These unstable loops can extend outwardly from the yarn bundle and adversely affect the yarn take off in subsequent textile mill operations. In fabrics made from such yarns, a "Velcro" or picky type characteristic may appear, and this is generally distasteful in apparel.
Methods are known for controlling these unstable loops to varying degrees. U.S. Pat. No. 4,338,776 (Krenzer) describes a process and apparatus for producing a crimped continuous multifilament yarn by the sequential steps of air-jet texturizing to form multiple random filamentary loops, immediately pulling out metastable loops formed in the yarn without heating and without stretching or deforming the yarn filaments, next shrinking and heat setting the yarn at a temperature of about 150.degree.-245.degree. C., and then winding the yarn onto a spool at a predetermined yarn tension. The non-crimped multifilament feed yarn is conducted through an air jet texturizing nozzle at an overfeed rate said to be sufficient to form multiple random loops in the individual filaments, including some proportion of unstable loops. Following passage through the air jet, the yarn is conducted to feed and draw rolls in a heat free condition such that at least some of the unstable loops are pulled out of the yarn.
Prior known methods of controlling the unstable or wild loops are generally expensive and marginally effective. The present invention provides an effective and inexpensive method and apparatus for producing air jet textured yarns with substantially no unstable or wild loops. One product of this invention results from the phenomenally high shrinkage inherent in cold-drawn partially oriented polyester, polyamide and similar yarns. The linear behavior of these yarns according to the invention is controlled by tension at the entrance and exit ends of a steam chamber wherein a modest latent stretch is deliberately retained in order to improve the transverse fiber properties resulting in enhanced fabric resilience.
The following definitions apply to terms of the art as used in this specification. The term "fully oriented yarn" denotes a polymeric yarn drawn to such an extent that its molecules are fully oriented and very little further extensibility is possible in a cold, i.e. unheated, condition without breaking. This is the most stable yarn condition, total recovery or relaxation occurs on heating in an unrestrained state, however there is a loss of transverse quality or resilience of the yarn.
"Undrawn yarn" denotes continuous filament yarn in a totally undrawn state of as-spun condition.
The term "partially oriented yarn" denotes a polymeric yarn drawn to an extent such that its molecules are somewhat or "partially" oriented, but the extent of draw is less than that for fully drawn yarn. The resilience of partially drawn yarn is improved compared to fully drawn yarn, resulting in improved wrinkle resistance in fabrics made from such yarn.
The term "spun yarn" as used herein denotes any yarn made from relatively short discontinuous yarn ends that are reconstituted by twist or other means to form continuous lengths of yarn of commercial usefulness. These yarns can be made of synthetics or of natural fibers such as cotton or wool.